1. Field of the Invention
This invention relates to a gusset bag for photographic photosensitive materials, which is particularly useful for packaging large solid photographic photosensitive materials, such as a rolled photographic paper, a roll film, superposed sheet photographic films and superposed sheet photographic papers.
2. Description of the Prior Art
Gusset bags are widely utilized as packaging bags for packaging various things. It is known in the art to prepare gusset bags made of paper, thermoplastic resin film and laminated sheet including the laminated sheet where a thermoplastic resin film layer is disposed on the inside so as to be heat-sealable (Japanese Patent KOKOKU Nos. 56-30177 and 58-54030, Japanese Utility Model KOKOKU No. 57-3789, etc.). A method of sealing the lower end of the bag by adhesive tape is also known (Japanese Patent KOKAI No. 56-5757).
On the other hand, photographic photosensitive materials are necessarily packaged in a packaging bag capable of shielding light completely, because photographic photosensitive materials lose their values upon exposure to light. Particularly, in the case of a heavy voluminous photographic photosensitive material having sharp edges, such as a rolled photographic paper, the double-sheet gusset bag shown in FIG. 11 was used. This double-sheet gusset bag was composed of the outer sheet A consisting of unbleached kraft paper 7 containing a paper strength increasing agent such as melamine resin, polyacrylamide resin, alkylketone dimer, etc. and a light-shielding thermoplastic resin film layer 6a as the heat-sealing layer and the inner sheet B consisting of a light-shielding low density polyethylene (LDPE) resin film layer 6a, an aluminum foil layer 5, bleached kraft paper layer 1' and another light-shielding LDPE resin film layer 6 .circle.a containing isobutylene rubber laminated in this order each through a LDPE resin adhesive layer 4. The light-shielding LDPE resin film layers 6a, 6 .circle.a of the inner sheet B do not affect adversely the photographic photosensitive materials packaged therein. Though the outer sheet A has the ability to affect the photographic photosensitive materials adversely, such as by fogging, its physical strength is large. It is also thermostable, and its printability is excellent. Moreover, the turned or rolled top and bottom seal portions can be fixed by using an adhesive or adhesive tape. The inner sheet B was incorporated in order to shield the adverse effect of the outer sheet A, to secure physical strength, moistureproofness and antistatic properties, and to prevent curling. Another inner sheet employed was, for example, the laminated film composed of an aluminum foil layer and two uniaxially stretched high density polyethylene resin layers containing carbon black having a particular draw ratio laminated on both sides of the aluminum foil layer each through an adhesive layer so that their orientation axes cross each other (U.S. Pat. No. 4,331,725). Another inner sheet was composed of a metallized film and two low pressure linear low density polyethylene (L-LDPE) resin film layers containing a light-shielding material laminated on both sides of the metallized film each through an adhesive layer (U.S. Pat. No. 4,663,218). The difference in the thickness of both L-LDPE resin film layers was within 50%.
As described above, conventional gusset bags for packaging photographic photosensitive materials were double-sheet gusset bags composed of an outer sheet and an inner sheet having different properties in order to secure physical strength, heat resistance, printability, writing quality, wear resistance, adhesive properties and the like under the conditions not affecting the photographic photosensitive materials therein adversely. As a result, they have various disadvantages. That is, since two packaging sheets of the outer sheet and the inner sheet were used, the packaging cost became expensive. They made the package bulky, and transportation increased, particularly when the package wax exported. The inventory of the packaging materials increased so as to require a larger area for maintaining the inventory. The cost for inventory control, orders to a packaging material distributor, purchasing cost of raw materials were also raised. It was also a hard work to align both edges of the outer sheet and the inner sheet under a safety light so as to not impair the quality of photographic photosensitive materials and to set them so as to pass the prescribed position of the pass roll of the processing machine. Moreover, since there is a space between the outer sheet and the inner sheet, the heat-sealing temperature of the gusset bag was necessarily high because of low heat conductance. Furthermore, since the unbleached kraft paper was brown, the gusset bags were heated under the sunlight whereby the quality of the photographic photosensitive materials occasionally degraded. The printing, color and appearance of the gusset bags were not good, and moreover, the paper, adhesive tape and adhesive were sometimes separated. During transportation, paper powder was generated due to rubbing with corrugated board box, and adhered to the gusset bag. The paper powder adhered to the surface of the photographic photosensitive materials at the time of removal in a dark room, and caused spot-shaped development defects.